def Unknown(X, Y):
    if X < Y:
        print(str(X + Y))
        return Unknown(X + 1, Y) * 2
    elif X == Y:
        return 1
    else:
        print(str(X + Y))
        return int(Unknown(X - 1, Y) / 2)


def IterativeUnknown(X, Y):
    Total = 1
    while X != Y:
        print(str(X + Y))
        if X < Y:
            X = X + 1
            Total = Total * 2
        else:
            X = X - 1
            Total = int(Total / 2)
    return Total


print("10 and 15")
print(str(Unknown(10, 15)))
print("10 and 10")
print(str(Unknown(10, 10)))
print("15 and 10")
print(str(Unknown(15, 10)))


print("10 and 15")
print(str(IterativeUnknown(10, 15)))
print("10 and 10")
print(str(IterativeUnknown(10, 10)))
print("15 and 10")
print(str(IterativeUnknown(15, 10)))